One of the more challenging design constraints placed on radio frequency (RF) engineers is the effective isotropically radiated power (EIRP) specification to which wireless transmission systems may conform. Existing methods and systems for complying with EIRP regulations are problematic. In the industrial, scientific, and medical (ISM) frequency band, for instance, the Federal Communications Commission (FCC) requires that a non-standard RF connector be used at the antenna port to ensure that a wireless device is not attached to an antenna that would cause the device to exceed applicable EIRP limits.
However, as a non-standard connector is put to common use in a family of devices, it eventually may lose its status as being “non-standard” over time. This may make the notion of what is non-standard difficult to determine and follow, especially because the FCC from time to time issues updated guidelines changing the status of certain non-standard connectors to standard.
Furthermore, for the personal communication service (PCS) band, no such formal requirement has been developed. Hence, a PCS wireless device user may connect an unauthorized antenna to the device and may cause an EIRP violation. In addition to EIRP compliance issues, permanent damage to a wireless device's internal components may result from prolonged operation with an unauthorized (i.e., mismatched) antenna.
A device may sustain as much damage when operated without an antenna as it might with a faulty antenna having an electrical short. A voltage standing wave ratio (VSWR) protection circuit may be deployed for circuit protection. In any of the above cases, early detection and prevention are needed to protect the device's power amplifier (PA) and other circuit elements from damage.